Neuro Pathogens Flashcards
Nervous system infections target what?
- Most commonly involve the CNS
- Peripheral nerve
- Target site for infectious processes & microbial toxin action
- Entry site of pathogens/toxic products that act on CNS
Why is minimizing the inflammatory response of the nervous system important?
- inflammation can lead to profound/irreversible disturbance in neuronal function
this is regulated by immunosuppressive mechanisms:
- Glial cells: secrete IL-6, TGFbeta2
- Induction of T cell apoptosis
What are the natural barriers against nervous system infections?
- Pathogen or product must reach nervous system
- must penetrate or interrupt anatomic barrier
- establish and persist by evading immune defenses
Describe the characteristics of nervous system infections
- most involve brain or meninges
- other sites may be co-involved or act as targeted site
- spinal cord involvement rare, d/t decr blood flow
- Microbial toxins can act even if pathogen not present
- injury from direct cytotoxic effects, inflammatory response, or both
What are the routes of infection for nervous system infections?
-
Hematogenous most common
- enter via choroid plexus, meninges, parenchyma, septic emboli in vessels that damage vascular endothelial cells
- retrograde movement within neurons
- extension of infectious process from contiguous sites (sinuses, tooth roots, middle ear, vert discs)
- can be secondary to migrating grass awns/FBs, deep bite wounds, trauma near head/spine
- iatrogenic from contaminated spinal needles/instruments
- if spinal taps are performed on animals w/ bacteremia
What are the clinical signs of a nervous system infection?
depends on localization of infection, agent, microbial toxin(s) present, and type/degree of inflamm response
- meninges - neck rigidity, depressed mental state
- cerebrum - circling, behavioral changes, seizures
- brainstem - CN deficits, head tilt
- cerebellum - ataxia, tremors
- spinal cord - tetra/paraplegia
Describe the characteristics of meningitis and encephalitis
- Often seen simultaneously (meningoencephalitis)
- CS of meningitis often precede those of encephalitis
- incidence of these diseases is fairly low compared w/ infections of other organs d/t the better protection of nervous system by its barriers
What are the clinical signs of meningitis?
- Fever
- hyperesthesia
- Neck rigidity
- painful paraspinal muscle spasms
- dogs display this syndrome acutely and sometimes chronically w/o CS of brain or spinal cord involvement
How do you diagnose meningitis?
CSF analysis
- CSF should be collected whenever:
- Hx or species/breed predisposition suggests meningitis or encephalitis
- CS indicate a disseminated or multifocal CNS disorder
What are two viruses that target the nervous system of both dogs and cats?
What is a fungal agent that targets the nervous system of both dogs and cats?
What are 3 viruses that target the nervous system in dogs only?
What are 4 viruses that target the nervous system in cats only?
What are 5 bacterial agents that cause nervous system infections in only dogs?
What are the guidelines for treatment of nervous system infections?
- Prognosis is guarded
- treatment = often of little benefit EXCEPT
- animals w/ probable immune-mediated, steroid-responsive CNS dz
- animals w/ meningoencephalitis caused by rickettsia and certain bacteria
